The issue is you have lighttpd running on port 80 (probably a leftover from a previous Pi-hole v5 install).
If you need to keep lighttpd, you have 2 options:
- change
lighttpdport (to something different than 80) or - change pihole port.
If you are not using lighttpd, you can safely disabled it (or even uninstall it) and restart pihole-FTL.
EDIT:
I just noticed you are already using port 8080 for pihole-FTL (I think this is automatically set when port 80 is in use):
port = "8080,[::]:8080,443s,[::]:443s" ### CHANGED, default = "80,[::]:80,443s,[::]:443s"
You can access the web interface using using http://pi.hole:8080/admin.
If you want to use port 80, you will need to disable lighttpd and change /etc/pihole/pihole.toml to use port 80.